Some electric vehicles use rechargeable batteries, electric motors, and motor controllers for propulsion. Some electric vehicles can only be driven a limited distance (e.g., between 40 to 100 miles) due to the low amount of energy that can be stored in the rechargeable batteries. The range of an electric vehicle can depend not only on the type of batteries used but also the weight of the vehicle, among other things. Once the batteries are discharged, they must be recharged before the electric vehicle can be used again. However, the battery recharge time can be relatively long (e.g., up to 6 to 8 hours). In typical use, the rechargeable batteries of an electric vehicle are charged overnight or any other time that the electric vehicle is not in use for a long period of time. Electric vehicles typically charge from conventional power outlets or charging stations.
U.S. Pat. No. 6,456,040 discloses a purported method of extending the battery life of rechargeable batteries used in electric vehicles. The '040 patent discloses that to preserve good battery life, it is essential to allow the recharging batteries used in electric vehicles to fully discharge and enter a deep discharge state before recharging. Accordingly, the '040 patent discloses the use of at least two battery banks. Instead of charging a partially discharged battery bank overnight each night in the traditional way, the '040 patent discloses using at least two battery banks. The first battery bank is used to power the vehicle until it has fully discharged while the second bank (i.e., the standby battery bank), which has been charged in the traditional way, is on standby to power the vehicle when the first battery bank becomes fully discharged. When the first battery bank fully discharges, the second bank then is used to power the vehicle and the first bank then is charged overnight in the traditional way.
The '040 patent discloses that the fully charged standby battery bank may need a “trickle charge” to maintain its fully charged status since charge may dissipate over time with certain battery types. Thus, the '040 patent also discloses a regenerative charging system for providing transient recharging of the standby battery bank only when the vehicle is braking or coasting (i.e., when the accelerator pedal is not engaged). The regenerative charging system using two generators, which are connected to the rim of a wheel of the vehicle via a belt and pulley system. The wheel also has a motor attached to it that drives the wheel.
The vehicle disclosed in the '040 patent may not be suitable for long range driving (i.e., driving beyond the cumulative range for each battery bank used in the vehicle) because the system only provides transient or regenerative charging of the batteries. Thus, once the standby battery bank is discharged the car is inoperative until recharged in the traditional manner. The transient recharging only during breaking and coasting is not sufficient to recharge a battery for continued driving.
Furthermore, the vehicle disclosed in the '040 patent appears to be inefficient. For example, the vehicle has four motors, one attached to each wheel of the vehicle, for driving the four wheels of the vehicle, respectively. Furthermore, the regenerative recharging system, which includes two generators, a belt, and a V-belt drive wheel pulley, is connected to the rim of one of wheel. Thus, the vehicle includes a number of components that can add to the weight to the vehicle thereby reducing the range of the batteries and increasing the cost of the vehicle.
As another example, the belt and V-belt drive wheel pulley adds friction to the system thereby reducing the efficiency of the recharging system. Still further, having the recharging system attached to the rim of one of the wheels may reduce the efficiency of the generator. Moreover, having the recharging system attached to the rim of one of the wheels can create a driving hazard if a generator was to engage at medium to high speeds (e.g., greater than 20 mph).